Electron beam devices, in particular a scanning electron microscope (hereinafter also referred to as an SEM) and/or a transmission electron microscope (hereinafter also referred to as a TEM), are used for examining objects (specimens), in order to gain insights into the properties and behavior under certain conditions.
In the case of an SEM, an electron beam (hereinafter also referred to as a primary electron beam) is generated by means of a beam generator and focused by a beam guiding system onto an object to be examined. By means of a deflecting device, the primary electron beam is guided in the form of a raster over a surface of the object to be examined. The electrons of the primary electron beam thereby interact with the object to be examined. As a consequence of the interaction, in particular electrons are emitted from the object (known as secondary electrons) and electrons of the primary electron beam are backscattered (known as backscattered electrons). The secondary electrons and backscattered electrons are detected and used for image generation. An imaging of the object to be examined is thus obtained.
In the case of a TEM, a primary electron beam is likewise generated by means of a beam generator and focused by means of a beam guiding system onto an object to be examined. The primary electron beam radiates through the object to be examined. During the passage of the primary electron beam through the object to be examined, the electrons of the primary electron beam interact with the material of the object to be examined. The electrons passing through the object to be examined are imaged onto a luminescent screen or onto a detector (for example a camera) by a system consisting of an objective lens and a projection lens. The imaging may in this case also take place in the scanning mode of a TEM. Such a TEM is generally referred to as an STEM. In addition, it may be envisaged to detect electrons backscattered at the object to be examined and/or secondary electrons emitted by the object to be examined by means of a further detector, in order to image an object to be examined.
It is also known from the prior art to use combination devices for the examination of objects, devices in which both electrons and ions can be guided onto an object to be examined. For example, it is known to equip an SEM additionally with an ion beam column. An ion beam generator arranged in the ion beam column is used as a means for generating ions that are used for the preparation of an object (for example ablating material of the object or applying material to the object) or else for imaging. The SEM serves here in particular for observation of the preparation, but also for further examination of the prepared or unprepared object.
In a further known particle beam device, application of material to the object is performed for example by using the feeding of a gas. The known particle beam device is a combination device, which provides both an electron beam and an ion beam. The particle beam device has an electron beam column and an ion beam column. The electron beam column produces an electron beam, which is focused onto an object.
The object is arranged in a specimen chamber kept under a vacuum. The ion beam column produces an ion beam, which is likewise focused onto the object. By means of the ion beam, for example a layer of the surface of the object is removed. After removal of this layer, a further surface of the object is exposed. By means of a gas feeding device, a gaseous preliminary substance—known as a precursor—can be admitted into the specimen chamber. It is known to form the gas feeding device with a needle-shaped device, which can be arranged quite close, at a distance of a few μm, from a position of the object, so that the gaseous preliminary substance can be guided to this position as accurately as possible. By interaction of the ion beam with the gaseous preliminary substance, a layer of a substance is deposited on the surface of the object. For example, it is known to admit gaseous phenanthrene into the specimen chamber through the gas feeding device as the gaseous preliminary substance. Then it is substantially a layer of carbon or a carbon-containing layer that is deposited on the surface of the object. It is also known to use a gaseous preliminary substance that compries a metal, in order to deposit a metal on the surface of the object. However, the depositions are not restricted to carbon and/or metals. Rather, any desired substances may be deposited on the surface of the object, for example semiconductors, nonconductors or other compounds.
In order that sufficient carbon or metal can be deposited on the surface, it is desirable to arrange the needle-shaped device of the gas feeding device as close as possible to the position on the surface of the object at which the layer is to be deposited. It is accordingly desirable to position the needle-shaped device as well as possible and to align it with the desired position of the surface of the object. However, the accurate positioning of the needle-shaped device often presents problems. Up until now, there has not been any reproducible procedure by which the needle-shaped device can always be arranged exactly at a specific position on the surface of the object. The previously known methods are in essence based on the principle of “trial and error”. Such a principle, however, is undesirable and disadvantageous. On the one hand, positioning the needle-shaped device at a specific position can take quite a long time. On the other hand, it is quite possible for errors to occur during the setting of the position, that is to say for there to be deviations from this position of the needle-shaped device, so that the needle-shaped device is not aligned sufficiently well with the position of the surface of the object. This can lead to a reduction in the gas density at the desired position of the surface of the object. This leads for example to a sparse and/or unreproducible deposition of a layer on the surface of the object.
Accordingly, it is desirable to be able to address the problem of providing a method and a particle beam device with which a component of a particle beam device, in particular a gas feeding device, can be positioned as accurately as possible at a specific position.